Electronic fuel injectors are frequently used in today's internal combustion engines. The electronic fuel injector provides precise and reliable fuel delivery into the cylinder of compression ignition and spark ignition engines. The precision and reliability of the electronic fuel injector have contributed to the goals of fuel efficiency, maximum practicable power output and control of undesirable products of combustion. These and other benefits of electronic fuel injection systems are well known and are appropriately used to beneficial effect in the design of modern internal combustion engines.
Known electronic fuel injectors, especially those designed for application in compression ignition or spark ignition engines, utilize means to enhance fuel charge pressurization. Enhanced fuel charge pressurization is desirable during the fuel injection event to assure proper atomization and spray distribution of the fuel into the engine cylinder or pre-chamber. In addition, it is desirable to be able to determine the quantity of fuel used and to control injection timing for several reasons, including obtaining full combustion of the fuel to control particulate emissions. This has been of great interest in recent years, owing to environment concern and regulatory incentives. Finally, the proper control of fuel injectors reduces the amount of residual particulate formed in the compression ignition engine cylinder.
Several known types of fuel injectors include a means to enhance pressurization of the fuel charge. These fuel injectors typically have mechanical linkage systems coupled to the engine camshaft and/or cylinder head valve train assembly. Such fuel injectors are configured so that the camshaft or other rotating or reciprocating member acts on an injector link either directly or indirectly through a rocker arm.
The injector body and the integral associated components of the fuel injector are generally installed in cavities provided in the engine cylinder head. The base of each cavity generally is ported directly to the engine cylinder fueled by that particular fuel injector or to a precombustion chamber for subsequent delivery to the engine cylinder.
Once installed, fuel is provided to the injector typically via a fuel rail or fuel supply manifold at a fuel pressure of 150 psi. The injector then draws in fuel according to the operating conditions of the engine, thus metering the fuel charge. After the fuel charge is properly metered, the injection cycle continues with the pressurization of the predetermined fuel charge. At a preselected pressure, an injector nozzle is caused to open and injection into the engine cylinder or equivalent structure begins. Pressurization continues until the predetermined injection interval has passed, upon which the pressure generated within the injector is relieved and the injection cycle is terminated. At the peak of the pressurization process, it is possible for fuel pressure to reach 23,500 psi. Thus, a structure capable of withstanding great mechanical stress is desired within the injector assembly itself and within the base cavity area.
The most common solution to this structural demand is to form the injector cavity so that the injector assembly must be press-fitted within the cavity. A very tight fit between the injector assembly and the cavity creates, initially, a leak proof interface capable of maintaining the very high pressures developed. After installation, the injector assembly is restrained by a holddown clamp which engages holddown clamp ears or projections located on the exterior surface of the injector assembly. The holddown clamp is then securely bolted to the base material, which prevents the injector assembly from becoming loose and thus maintain the initial press-fit.
Various means are employed to obtain the initial press-fit between the injector assembly and the base cavity. A hydraulic or pneumatic press may be used, but mechanical impact tools are most commonly employed. These tools have the advantage of being inexpensive and portable, which is especially important relative to the replacement or repair of the fuel injector assembly. Since these repair or replacement operations are performed outside of the production facilities and at remote sites, a portable hand tool capable of satisfactorily providing the necessary press-fit is preferred.
Recent changes in the layout and design of modern compression engines has created severe difficulties with the use of hand operated mechanical impact devices. As the result of various incentives, such as the need for improved engine efficiency and lower emissions from smaller power plants, manufacturers are trending toward multi-valve engine cylinders. The result of this trend is to reduce the distances between the various components making up the engine head assembly, such as the valves, valve springs, rocker arms, push rods, fuel injectors and associated hardware. Further, the configuration of newer fuel injectors has increased the size of the injector relative to previous versions. Thus, installation or subsequent removal of the fuel injector without damaging adjacent parts has become more difficult. In addition, misalignments and errors in the installation of the fuel injector leading to component interference have become more frequent and often has resulted in the reduced durability of the components involved. Interference is especially undesirable when the valve spring is allowed to physically contact another component, since the valve spring rate may be changed after the spring material wears under the repeated contact with the interfering component. In many cases, the interfering component is the fuel injector.
Often, the misalignments and errors encountered during the installation of fuel injectors are the result of poor visual alignment, which is often difficult when the engine is being serviced as installed in the vehicle after the vehicle is initially placed in service. Existing fuel injector installation tools do not provide guidance features for the proper alignment and orientation of the fuel injector and thereby require visual alignment.